Best way to make bone broth is to use a joint bone or a pig's foot or chicken feet. That way you have cartilage and connective tissue to create the gelatin. You put it in the slow cooker with water and salt and if you want, some spices and even some onions and celery if you want even more flavors. Then you wait a day for it too cook. Throw out the solid stuff, let the broth cool so the fat rises to the top and congeals. You can either remove and discard the fat, use it for cooking or keep it in your broth.